1. Technical Field
The present invention relates to optical connectors in general, and in particular to a fiber-optic connector having an embedded window for connecting an optical fiber to other optical assemblies.
2. Description of Related Art
A fiber-optic connector is typically utilized to connect an optical fiber to other optical assemblies. A fiber-optic connector commonly includes a ferrule in which an internal optical fiber is housed.
The profile of the end face of an optical fiber can significantly affect its connection characteristics. For example, when an angle (i.e., an angle to the optical fiber axis) of the end face of an optical fiber deviates from a right angle or the end face of an optical fiber is highly roughened, air may enter in a space between the end face of the optical fiber to any subsequent optics. As a result, Fresnel reflection increases at the end face of the optical fiber, and leads to an increase in connection loss of the optical fiber.
One method for preventing the increase in connection loss of an optical fiber due to the roughness of the end face of the optical fiber is by polishing the end face of the optical fiber. However, this method is not suitable when the external optical fiber (such as holey fiber or soft glasses) is very sensitive or when the connection work is conducted at the setting site of the optical fiber because of the necessity of a polishing device and high labor cost.
Another method is to use a refractive index matching agent interposed between the end faces of optical fibers and subsequent optical surfaces. With this method, air can be prevented from entering into the space between the end faces of the two optical fibers. As a result, Fresnel reflection caused by the air can be lowered, and the connection loss of optical fibers can be reduced. However, this method has the following problems. Since the refractive index matching agent is generally formed of a silicone or paraffin agent in liquid or grease state, it can cause undesirable contamination (to holey fibers or high-power fibers). Furthermore, since the refractive index matching agent generally has a temperature dependency in refractive index, transmission loss of optical fibers may vary according to a change in refractive index of the refractive index matching agent. Also, current index matching agents are typically restricted to wavelengths below two microns due either to low refraction index (most have n<1.8) or low transmission index at longer wavelengths.
Yet another common method for reducing Fresnel reflection loss is to treat the surface of an optic fiber with an anti-reflective coating after its assembly into a ferrule. This coating can be applied via vapor deposition. Alternatively, the surface can be mechanically altered to achieve the same effect (i.e., moth-eye microstructure). Unfortunately, some optical fiber materials, such as mid-infrared sensitive glasses, in high-power applications may be unsuitable for this method.
Due to the impracticality of implementing traditional methods for reducing Fresnel reflection loss in certain types of optical fibers, an improved fiber-optic connector would be desirable.